Concept preview

What you will be able to do

1. 01Describe binary fission and explain why it produces identical clones.
2. 02Explain bacterial exponential growth and the phases of a growth curve.
3. 03Describe how bacteria gain genetic variation without sexual reproduction.
4. 04Describe the metabolic diversity of bacteria and its importance to ecosystems.

Bacteria reproduce by binary fission, a simple form of asexual reproduction. The single circular chromosome is copied, the two copies move to opposite ends of the cell, the cell grows longer, and then it pinches in the middle to split into two identical daughter cells. Because there is only one parent and no mixing of DNA, the daughters are genetic clones of the parent. What makes this astonishing is the speed: under good conditions a bacterium such as E. coli can divide roughly every 20 minutes, so one cell becomes two, then four, then eight — and within a day could, in theory, outnumber every star in the galaxy.